A minimum 100 mm deep layer of clean 5 to 20 mm diameter angular or rounded stone (e.g. High Performance Bedding, HL-6, pea gravel) should be placed on top of the coarser storage reservoir aggregate to prevent downward migration of filter media into the reservoir and pipe. See [[Aggregates]] for further details. | A minimum 100 mm deep layer of clean 5 to 20 mm diameter angular or rounded stone (e.g. High Performance Bedding, HL-6, pea gravel) should be placed on top of the coarser storage reservoir aggregate to prevent downward migration of filter media into the reservoir and pipe. See [[Aggregates]] for further details. |